required by the purpose of the project and thatthe compilation be completed with sufficient leadtime. Generally, a separate folder for each projectis maintained and labeled.Some of the engineering data that may beconsidered for SEABEE projects are as follows:Vicinity maps, topographic maps, oraerial photographs of the siteGeographic factors, accessibility, realestate, and so forthGeographic location: latitude andlongitude; control points (both horizontal andvertical)Tide informationWeather and climatic conditions: rainfall,wind velocity (including direction and duration),flood, and perhaps typhoon or hurricane seasonsCurrent velocity and discharge of a riveror stream and perhaps an estimate of thewatershed areaTypes of soils and their natural conditions(samples may be collected for testing)Availability of construction materials, suchas rocks, gravel, sand, borrow pits, and timber,near the siteAvailability and suitability of local laborand existing facilities, such as sources of power,water, and other utilitiesOther factors affecting construction,military operations, and logistics supportFactors Affecting FieldworkThe surveyor must constantly be alert to thedifferent conditions encountered in the field.Physical factors,such as TERRAIN ANDWEATHER CONDITIONS, affect each fieldsurvey in varying degrees. Measurements usingtelescopes can be stopped by fog or mist. Swampsand flood plains under high water can impedetaping surveys. Sights over open water or fieldsof flat, unbroken terrain create ambiguities inmeasurements using microwave equipment. Thelengths of light-wave distance in measurementsare reduced in bright sunlight. Generally,reconnaissance will predetermine the conditionsand alert the survey party to the best method touse and the rate of progress to expect.The STATE OF PERSONNEL TECHNICALREADINESS is another factor affecting field-work. As you gain experience in handling varioussurveying instruments, you can shorten surveytime and avoid errors that would require resurvey.The PURPOSE AND TYPE OF SURVEY areprimary factors in determining the accuracyrequirements. First-order triangulation, whichbecomes the basis or “control” of future surveys,is made to high-accuracy standards. At the otherextreme, cuts and fills for a highway survey carryaccuracy standards of a much lower degree. Insome construction surveys, normally inaccessibledistances must be computed. The distance iscomputed by means of trigonometry, using theangles and the one distance that can be measured.The measurements must be made to a high degreeof precision to maintain accuracy in the computeddistance.So, then, the purpose of the survey determinesthe accuracy requirements. The required accuracy,in turn, influences the selection of instruments andprocedures.For instance, comparatively roughprocedures can be used in measuring forearthmoving,but grade and alignment of ahighway have to be much more precise, and they,therefore, require more accurate measurements.Each increase in precision also increases the timerequired to make the measurement, since greatercare and more observations will be taken.Each survey measurement will be in error tothe extent that no measurement is ever exact. Theerrors are classified as systematic and accidentaland are explained in the latter part of this text.Besides errors, survey measurements are subjectto mistakes or blunders. These arise frommisunderstanding of the problem, poor judgment,confusion on the part of the surveyor, or simplyfrom an oversight. By working out a systematicprocedure, the surveyor will often detect a mistakewhen some operation seems out of place. Theprocedure will be an advantage in setting up theequipment, in making observations, in recordingfield notes, and in making computations.Survey speed is not the result of hurrying; itis the result of saving time through the followingfactors:1. The skill of the surveyor in handling theinstruments2. The intelligent planning and preparation ofthe work11-5
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